Endoscope apparatuses wherein a scope is inserted into a coelom in order to observe portions of the alimentary canal such as the esophagus, the stomach, the small intestine, and the large intestine, or into the trachea and the lungs for observing images on a TV monitor screen are commonly utilized. Recently, the use of illumination light of specific wavelength ranges for observing in vivo tissue has started to become popular. For example, an endoscope apparatus has been proposed for more easily identifying lesions that are difficult to discern with normal observation light which utilizes the phenomenon that in vivo tissue emits fluorescence when illuminated by light of specific wavelengths. Furthermore, attempts have been made to gather detailed information of lesions by utilizing the light absorbance properties and the light scattering properties of in vivo tissues to light of different wavelength ranges. For example, Japanese Laid Open Patent Application H08-140929 discloses an apparatus which can switch between providing an ordinary color image observation and a fluorescent image observation of a lesion. At the tip of the endoscope are installed one image sensing chip that detects ordinary color images and a separate image sensing chip that detects fluorescent light images.
As another example, Japanese Laid Open Patent Application 2001-170009 discloses an apparatus which can switch between providing an ordinary color image observation and the observation of blood vessel structure at various depths from the surface of a lesion. In this apparatus, a light source unit is used which provides different illumination light for the two kinds of observations.
As another example, Japanese Laid Open Patent Application 2000-41942 discloses an apparatus which can switch between providing ordinary color image observation verses infrared image observation of a lesion. In this apparatus as well, a light source unit is used which provides different illumination light for the different kinds of observations. This endoscope apparatus can provide two kinds of observations using different specialized infrared illuminations as well as provide an ordinary color image observation. However, when performing a precise diagnosis or treatment of a lesion by combining three kinds of observations, three kinds of endoscope apparatuses have to be prepared. Because of this, there is a shortcoming in that it is troublesome to have to change the endoscope apparatus every time the kind of special light observation is changed, and such a procedure increases the time required for such an endoscopic examination. Also disclosed in this prior art example is a device for performing individual special light observations effectively and efficiently. However, there is no mention of a method and apparatus for diagnosing a lesion state correctly within a short period of time by combining special light observations. Namely, there is no disclosure of a device which allows the state of a lesion to be immediately determined without taking a pathological sample and having it examined in detail, after which a decision may be made for treatment.